I turned on -ffunction-sections and compiled with -Os. The size gain at -O2 is less though.
Bingfeng > -----Original Message----- > From: Xinliang David Li [mailto:davi...@google.com] > Sent: 29 April 2010 17:17 > To: Bingfeng Mei > Cc: Richard Guenther; gcc@gcc.gnu.org > Subject: Re: LTO question > > Just curious, what is the base line size of your comparison? Did you > turn on GC (-ffunction-sections -fdata-sections -Wl,--gc-sections)? > > David > > On Wed, Apr 28, 2010 at 2:44 AM, Bingfeng Mei > <b...@broadcom.com> wrote: > > Thanks, I will check what I can do with collect2. LTO > > seems to save 6-9% code size for applications I tested > > and should be very useful for us. > > > > Bingfeng > > > >> -----Original Message----- > >> From: Richard Guenther [mailto:richard.guent...@gmail.com] > >> Sent: 28 April 2010 10:33 > >> To: Bingfeng Mei > >> Cc: gcc@gcc.gnu.org > >> Subject: Re: LTO question > >> > >> On Tue, Apr 27, 2010 at 6:30 PM, Bingfeng Mei > >> <b...@broadcom.com> wrote: > >> > Hello, > >> > I have been playing with LTO. I notice that LTO doesn't work when > >> > object files are achived into static library files and the final > >> > binary is linked against them, although these object files > >> are compiled > >> > with -flto and I can see all the lto related sections in > .a files. > >> > Is this what is described in LTO Wiki page? > >> > > >> > "As an added feature, LTO will take advantage of the > plugin feature > >> > in gold. This allows the compiler to pick up object > files that may > >> > have been stored in library archives. " > >> > > >> > So do I have to use gold to solve this issue? > >> > >> Yes. Or you fix collect2 to do processing of archives and hand > >> lto1 the required information (it expects archive components > >> with LTO bytecode like archiv...@offset with offset being the > >> offset of the .o file with LTO bytecode inside the archive). See > >> lto/lto-elf.c:lto_obj_file_open for "details". > >> > >> Richard. > >> > >> > Many thanks, > >> > Bingfeng > >> > > >> > >> > > > >
